Variable displacement pump



' JNVNTOR.

F. A. SNELL VARIABLE DISPLACEMENT PUMP Filed NOV. 6, 1955 May 21, 19574. 4 l. f f A 7 S m.\ AKW@ m ,m Alf N A 7 nited States Patent l i i2,792,687 VARIABLE DEPLACEMENT PUMP Francis A. Snell, Proctorsville,Vt., assigner to tlre United States of America as represented by theSecretary of the Air Force Application Novemberu, 1953, Serial No.390,768

3 Claims. (Cl". dll-$4.15)

This invention is directed to a novel variable displacement pulsatortype of pump of an improved nature. The practical embodiment of theinvention described herein is particularly applicable, for example, fordriving an hydraulically operated shake table for testing seismologicalinstruments. While single acting as shown, it may be either single ordouble acting as the application may require. Its construction is suchthat the single unit affords a wide range of amplitude of impulsetransmission without any lost motion presenting simplicity, economy andeiciency in its operation.

The improved pump comprises a housing having an hydraulic chamber with amultiplicity of pistons of varying diameter mounted for reciprocationtherein selectively whereby on reciprocation of a piston of particulardiameter a predetermined amount of fluid is displaced from the housingto afford a predetermined control signal of a desired amplitude.

An object of the invention is to provide an improved variabledisplacement pulsator type pump.

A further object of the invention is to provide a novel variabledisplacement pulsator type pump employing a multiplicity of selectivelyoperable pistons having a range of varying diameters whereby a selectivedisplacement may be accomplished by the pump to afford a desiredcontrol.

Other objects and advantages o' the invention will be readily apparentto those versed in the art from the following specification taken inconjunction with the accompanying drawings wherein:

Fig. 1 shows the improved variable displacement pump in partial sectionin conjunction with a control unit;

Fig. 2 is a section along line 2 2 of Fig. 1 and shows the detentarrangement for locating the actuator relative to the piston housing forpositive control of the pump displacement;

Fig. 3 shows a section indicated by line 3--3 in Fig. 1;

Fig. 4 shows a section on line 4 4 in Fig. 1.

As shown in Figure 1 of the drawings the improved pump comprises apiston housing 1 incorporating an oil chamber 2 at one end thereof. Theother end of the piston housing is bolted to an actuator unit 3. Aconduit connects the oil chamber 2 with a control unit 4.

The piston housing assembly in the practical embodiment of the inventionshown has three bore holes 5 equidistantly spaced therein each havingthe bore red-ced by a bearing member 6, each bearing member having anaperture of a different diameter extending through to the oil chamber Z.Respectively arranged in the bores 5 are three pistons 7, 8 and 9 whosereduced portions 7', 8 and 9', each having a different diameter, bear inand extend through the corresponding bearing elements 6 threadedlyengaging the housing. The stem extension on each piston has a collar liladjacent one end thereof to bear in the respective bore hole S and guidethe movement of the piston. A coil spring 11 surrounding each pistonabuts the collar and the housing and the bearing element 6, biasing thepistons by a force against 2,792,687 Patented May 21, 1.957

thecollar members. Thel pistons are normally arranged so that their`extensions are ilush with the actuator end of the piston housing asshown in Figure 1 of the drawings. At the actuator end of the pistonhousing assembly isa flange and equidistantly arranged` about andadjacent the periphery are threaded holes 12.

The actuator assembly is` composed of a sleeve unit 13 having a ange 14by which the actuator unit is bolted to the piston housing throughmatching holes 12. With* inthe sleeve unit 13 and rotatable relativethereto is an inner sleeve 15` having a iiange 16 in threaded engagementtherewithV to seat on the stepped portion of the outer sleeve unit 13asshown in Figure 1. A plate 17 integral with the sleevelS has asinglehole `17 therethrough arranged to align selectively with the threepiston stems 7, 8 and 9 in the piston housing. The inner sleeve at itsouter end has a flange 18 bearing on the llange 14 on outer sleeve end.Connected to the flange 18 in a recess therein is a spring presseddetent 19. Spaced notches 19 in the outer sleeve member ilange 14',arranged to conform to the spacing of the pistons, cooperate with thespring detent to hold the rotatable sleeve 15 in predetermined positionsrelative to the pistons to align the hole 17 with a selected piston. Aplunger unit 2t) within the inner sleeve has a pin 21 threadedly relatedthereto and extending therefrom guided in the hole in the plate 17. Ayoke 22 is connected to the outer end of the plunger which is rotatablerelative thereto on a stem 22 from the yoke connected to the plunger andthe yoke has bearing plates 23 of a hardened material thereon. The yokeis operated by an eccentric 24 having an outer ball bearing fittingclosely between the bearing plates 23.

When the actuator assembly and the piston housing assembly areassembled, the ends of the pistons 7, 8 and 9 adjacent the actuator unitare flush with the bolted together faces of the piston housing and theflange 14 of the sleeve of the actuator housing. This permits the pin 21with its connected sleeve and plunger to be rotated freely relative tothe pistons being limited only by the detent 19 engaging a notch 19whereby the pin Z1 is -aligned with a piston 7, 8 or 9 of the desireddiameter.

The operation of the pump unit is effected by rotating the sleeve andplunger unit of the actuator assembly to align the pin 21 with theselected piston 7, S or 9 of a particular diameter. The pistons notselected will not atleet the motion imparted in the hydraulic systemsince they are held against movement by their springs 11 against theplate 17 integral with the inner sleeve 15.

The eccentric element 24 imparts a simple harmonic motion to the plunger20 to actuate the selected piston to displace a predetermined amount offluid in the hydraulic system to provide the required amplitude ofmotion to the control unit 4 of the hydraulically operated shake tableas evidenced by the master cylinder in Figure 1 of the drawings shownconnected by a iiow line to the hydraulic cylinder 2 in which thepistons 7', 8 and 9 are operative to selectively displace apredetermined amount of uid dependent on their diameters.

While only three pistons of ditferent diameters have been employed inthe practical embodiment of the invention shown herein the number may bevaried to conform to the desired application. Many other modificationsand applications of the invention will be readily apparent to thoseversed in the art and such lie within the scope of the following claims.

What is claimed is:

l. A variable displacement pump comprising a piston housing providing ahydraulic chamber at one end thereof, pistons of dilerent diametersmounted in said housing for reciprocation therein, an actuator housing,a plunger assembly within the actuator housing having an actuating icepin at one end thereof adapted for selective alignment with the pistons,and means associated with the plunger assembly for selective alignmentof the plunger pin with the desired piston whereby on actuation of saidplunger a predetermined uid impulse maybe selectively'produced. v

2. A variable displacement pump comprising a piston housing, ahydraulicchamber at one end thereof having an opening for connecting the luid inthe chamber with a control means, pistons of different diametersarranged equidistantly about and reciprocable within the housing, asleeve connected to said piston housing and arranged coaxial therewith,a plunger assembly within the sleeve and rotatable with respect thereto,the plunger being reciprocable therein, motion transmitting means onsaid plunger adapted for selective alignment with the pistons ofdifferent diameters, and means for imparting motion to said plungermeans upon selective alignment of the motion transmitting means.

3. A variable displacement pump comprising a housing, hydraulic fluid inone end thereof, pistons of different diameters arranged in equallyspaced fashion from the central axis of the housing and reciprocabletherein, an actuator unit connected with the housing including plungermeans reciprocable to selectively actuate the pistons, means toselectively align the plunger means with a piston of a desired diameterwhereby on actuation of the plunger means a selected iluid displacementmay be obtained,

References Cited in the le of this patent UNITED STATES PATENTS GiulianoSept. 18, 1951

